Endocrine involvement in hibernation will be studied in the Turkish hamster. The ability of physiological quantities of androgen to terminate hibernation will be further examined. The serum concentrations of LH, FSH, prolactin and testosterone will be measured during hibernation to determine whether the pituitary-testicular axis is activated prior to the end of the period of hibernation. The ability of the testis of hibernating males to respond to exogenous gonadotropins will also be examined. The site of action of androgen in blocking hibernation will be investigated. The overall objective of these studies will be to establish the nature of the relationship between seasonal cycles in gonadal function and seasonal cycles in hibernation, respectively. A second set of experiments has been designed to determine whether a humoral factor(s) might be directly involved inducing dormancy and/or arousal from torpor in the Turkish hamster.